1. Field of the Invention
This invention relates to preservation of at least partially cooked potato pieces by treatment with sulfur dioxide and packaging to exclude microbial contamination and oxygen and to the related process.
2. Decription of the Prior Art
Sulfur dioxide gas and sulfur dioxide-containing salts have been incorporated in processes for the preservation of fresh fruits, vegetables, meats and the like, having low and intermediate moisture contents, see U.S. Pat. No. 1,061,460, issued May 13, 1913. In the dehydration of most vegetables, sulfur dioxide is used, (usually in the form of solutions of a sodium salt) to prevent oxidation and enzymatic discoloration during processing and to protect the dried products from nonenzymatic browning. In the drying of fruits, sulfur dioxide treatment is known to bleach the dark pigments resulting from enzymatic browning and subsequently protect the dried fruit from nonenzymatic browning.
Sulfur dioxide heretofore has not been used commercially to microbially stabilize partially cooked foods containing high moisture. The state of the art prior to this invention is summarized in the text Disinfection, Sterilization and Preservation Carl A. Lawrence and Seymour S. Block, Lea & Sebiger Publisher, 1968, which has an entire chapter devoted to GASEOUS STERILIZATION. The only reference to sulfur dioxide in the chapter is a statement at page 669 that it was used in the 19th Century as a means of fumigating sick rooms. Sulfur dioxide, however, is discussed at pages 639-640 in more detail in Chapter 39, entitled FOOD PRESERVATIVES. There it is stated that sulfur dioxide is used to "treat" fruits and vegetables before dehydration. Low concentrations of sulfur dioxide are also used to delay the decay of fresh grapes and inhibit undesirable bacteria in wine making without interfering with yeast action. Other prior art teachings involve subjecting various fresh fruits and vegetables to sulfur dioxide under pressure in excess of 5 psig in a closed chamber to enhance storage characteristics. Pre-peeled potatoes have heretofore been treated with minor concentrations of sulfite salt solutions to prolong their storage life under refrigeration. However, when significant concentrations of sulfur dioxide or its salts are used on raw prepared potato pieces, substantial potato cell destruction occurs, resulting in considerable fluid loss from the cells. As a consequence, commercially available potato pieces are either canned, refrigerated, frozen or dehydrated.
The prior art does not disclose or suggest means for producing high moisture potato products in the class of convenience foods which can be stored at ambient temperatures and which can be simply and quickly utilized to make a variety of potato dishes.
Frozen french fried potatoes are by far the biggest volume frozen food item sold in the United States. Over 2 billion pounds were sold in 1959. Such commercially available parfried products must be kept frozen throughout the distribution channels up to final heating prior to consumption. The inherent high cost is accepted since no other means has heretofore been developed for keeping the product microbially stable without such refrigeration. Prepeeled french fries are likewise sold in tremendous quantities. Such products must be held under refrigeration and even then have a limited storage life. The present invention allows ambient distribution and storage temperatures prior to use.